The composite glucose metabolism, polyol pathway activity, free and lipid-bound myoinositol concentrations and morphology of aortic intima-media from normal and alloxan diabetic rabbits will be compared by in vitro incubations of a preparation of aortic intima-media that retains an intact endothelium. Electron microscopic studies will compare the passage of intravenously injected ferritin and hydroxyferritin across the endothelial barrier in aorta, skeletal muscle and other organs in normal and streptozotocin diabetic rats, and in diabetic rats treated with insulin or a diet containing 1% myoinositol. The composite glucose metabolism, respiration, free and lipid-bound myoinositol of the neural components of peripheral nerve from normal and alloxan diabetic rabbits will be compared by incubations of preparations of an isolated nerve fascicle from sciatic nerve, and of its endoneurial components. Studies will be initiated to assess the relative importance of endogenous synthesis and active concentration in the maintenance of the high free myoinositol concentrations in these tissues and to clarify the origin of the decrease associated with experiemental diabetes.